Method for configuring a wireless distribution system and optimize method thereof

ABSTRACT

A method for configuring a wireless distribution system is provided. In the method, a target node starts a building procedure and begins to broadcast a building information. A joining node starts a scanning procedure for scanning all channels available and locks one channel used by the target node. The joining node sends a connect request signal and a channel assign request to the target node. The target node selects one link and one channel available for the joining node for communication, and sends a channel reset signal to the joining node. The MAC address of the joining node is added into an internal table of the target node. After the joining node has received the channel reset signal, the MAC address of the target node is stored into an internal table of the joining node, and the designated link channel is configured.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 94133513, filed on Sep. 27, 2005. All disclosure of theTaiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a method for configuring a wirelessdistribution system and optimize method thereof. More particularly, thepresent invention relates to a method for configuring a wirelessdistribution system and optimize method thereof, wherein a new wirelessdistribution system link is dynamically added such that the wirelessdistribution system network can give the optimized performance.

2. Description of Related Art

Distribution System (DS) is defined in IEEE802.11 specification as asystem for linking two different Basic Service Sets (BSS). Referring toFIG. 1, for BSS3 and BSS4 in the right half, the manner of linking theirAccess Points (AP) BSS3AP and BSS4AP with network cables is referred toas a DS. And for BSS1 and BSS2 on the left half, their APs BSS1AP andBSS2AP are linked in a wireless manner, which is referred to as aWireless Distribution System (WDS).

The wireless AP having the WDS function is different from a common AP inthat it has multiple roles, i.e. besides for serving the mobile clients,it can also be WDS linked with other APs directly, to expand theexisting service range of the wireless network. As shown in FIG. 1,BSS3AP (the AP of BSS BSS3) builds a WDS link (WDS Link2 as shown) withBSS1AP (the AP of BSS BSS1), and also builds another WDS link (WDS Link1as shown) with BSS2AP (the AP of BSS BSS2), so the AP BSS4AP cancommunicate with the AP BSS2AP through the forwarding of the WDS. Andthe notebook connected to the AP BSS2AP (bss1NB as shown) can also belinked to the wired network on the right through the WDS.

Since the network cards at the same wireless AP have to use the samechannel, the two BSSs linked through the AP have to use the samechannel, and that is the reason why BSS1, BSS2 and BSS3 all use the samechannel in FIG. 1.

The operation of the WDS is to communicate with each other through aframe including four addresses. Referring to FIG. 2A, the frame includesseveral fields such as a Frame Control field, a Duration/ID field, anAddress 1 field, an Address 2 field, an Address 3 field, a SequenceControl field, an Address 4 field, a Frame Body field and a Frame CheckSequence (FCS) field. In the frame, the numbers of Octets in each fieldare respectively: 2 Octets in the Frame Control field, 2 Octets in theDuration/ID field, 6 Octets in the Address 1 field, 6 Octets in theAddress 2 field, 6 Octets in the Address 3 field, 2 Octets in theSequence Control field, 6 Octets in the Address 4 field, 0˜2312 Octetsin the Frame Body field, and 4 Octets in the FCS field.

The content in the four address fields are as shown in FIG. 2respectively. The WDS frame in the drawing includes SA representing amedia access control (MAC) address of a source terminal, DA representinga MAC address of a destination terminal, TA representing a MAC addressof an AP for forwarding frames, and RA representing a MAC address of areceiving terminal AP.

Taking FIG. 1 as an example, if a client terminal bss2NB connected withthe access point BSS2AP within BSS2 is going to send data to anotherclient terminal bss1NB connected with the access point BSS1AP withinBSS1, the frame content will includes in sequence: the MAC address ofthe BSS1AP, the MAC address of the BSS2AP, the MAC address of thedestination client bss1NB and the MAC address of the source clientbss2NB.

The BSS2AP inquires through a WDS table of itself, forwards the frame toBSS1AP, and then sends it to the destination client bss1NB.

The following is the flow of configuring a WDS in the prior art:

(1) Before configuration, inquire and write down the wireless MACaddresses of the access point BSS1 AP and the access point BSS2 AP.

(2) Start the WDS function of BSS1 AP and BSS2 AP.

(3) Add each of the MAC addresses to the WDS Table of the other party.

(4) Configure two APs for using the same channel.

(5) Restart.

The existing wireless network AP have to configure its MAC Table andadjust the Channel settings manually when configuring the WDS Link,meanwhile, it can not perform optimize when adding or reducing thenodes.

SUMMARY OF THE INVENTION

Accordingly, the present invention directs to provide a method forconfiguring WDS, wherein the steps of manual configuration can bereduced, and new WDS links can be added dynamically, to optimize theperformance of the WDS network.

In an embodiment of the present invention, a method for configuringwireless distribution system is provided. In the method, a target nodestarts a building procedure and begins to broadcast a buildinginformation. A joining node starts a scanning procedure for obtainingand locking one channel used by the target node. The joining node sendsa connect request signal to the target node. The target node selects onelink and assigns it to the above joining node, and then sends a connectacknowledge signal to the above joining node. The joining node sends achannel assign request to the above target node, requiring the targetnode to assign a channel. The target node selects a channel availableand sends a channel reset signal to the joining node. The MAC address ofthe joining node is stored into an internal table of the target node.After the joining node has received the channel reset signal, the MACaddress of the target node is stored into an internal table of thejoining node, and the designated link channel is configured.

In the above-described method for configuring wireless distributionsystem, the scanning procedure of the joining node scans all channelslisted in a scan channel list, and after a scan report is obtained, itobtains and locks one channel used by the target node according to thescan report.

In the above-described method for configuring wireless distributionsystem, if the above target node has no available link to be assigned tothe above joining node, it will send a link assign failure signal to theabove joining node, and the target node and above joining node can notbe communicated with each other.

In the above-described method for configuring wireless distributionsystem, if the target node belongs to a first wireless distributionsystem network, and the joining node belongs to a second wirelessdistribution system network, when the joining node discoveries aconflict between channels according to the information of the targetnode, the joining node will unicast a channel conflict message to othernodes in the second wireless distribution system network and request forchanging the channels, and the other nodes having received the channelconflict message also send the unicast channel conflict message,furthermore, the joining node also requests other nodes to change theRoot node of the first wireless distribution system network as the Rootnode thereof.

In an embodiment of the present invention, a distributional optimizemethod for configuring a wireless distribution system network isprovided, which comprises notifying all nodes by broadcast to adjust tothe same channel by the Root node of the wireless distribution systemnetwork. This Root node sends optimize data to all nodes, and afterthese nodes have received the optimize data, they broadcast the optimizedata with their own information added. After a given time, they willstop sending the above optimize data and their own information, andselect a parent node from the received optimize data and the informationof other nodes. Then perform a joining procedure, and join into thewireless distribution system network architecture under the Rootdirectory.

In the above distributional optimize method for configuring, the abovejoining procedure is a method of joining a joining node into a targetnode, comprising sending a connect request signal to the target node bythe joining node. The target node selects a link and assigns it to thejoining node, then sends a connect acknowledge signal to the joiningnode. The joining node sends a channel assign request to the targetnode, for requesting the target node to assign a channel. The targetnode selects a channel available and sends a channel reset signal to thejoining node. The MAC address of the joining node is stored into theinternal table thereof. And after the joining node has received thechannel reset signal, the MAC address of the target node is stored intoan internal table thereof, and the above designated link channel isconfigured.

In the above distributional optimize method for configuring a wirelessdistribution system network, the optimize data comprising the channelsavailable for the Root node, the number of the links available, and thepower of the Root node and the like.

In an embodiment of the present invention, a central control optimizemethod for configuring a wireless distribution system network isprovided, which comprises notifying all nodes by broadcast to adjust tothe same channel by a Root node of the wireless distribution systemnetwork. The Root node sends a Discovery message requesting the abovenodes to provide information, and the above nodes reply the message toacknowledge their reception. Each node having received the discoverymessage will send its information back to the Root node. And the Rootnode performs calculation according to those received node informationand sends the result to each node, while each node rebuild a wirelessdistribution system link according to the result sent by the Root node,thereby to realize an optimized configuration.

In the above central control optimize method for configuring a network,the optimize data comprising the channels available for the Root node,the number of the links available, and the power of the Root node andthe like.

In order to the make the aforementioned and other objects, features andadvantages of the present invention comprehensible, a preferredembodiment accompanied with figures is described in detail below.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic view of distribution system (DS) architecture andwireless distribution system (WDS) architecture.

FIG. 2A shows a frame architecture containing four addresses of the WDS.

FIG. 2B shows the content of the four address fields in the WDS framearchitecture of FIG. 2A.

FIG. 3A shows a schematic view of a network architecture wherein node Bis to be joined into the existing WDS group, and linked with node A.

FIG. 3B shows the process flow of building a new link between node A andnode B according to a preferred embodiment of the present, includingScanning procedure, Building procedure and Joining procedure.

FIG. 3C shows the process flow of building a new link between node A andnode B if an error occurs.

FIG. 4A shows a schematic view of a network architecture wherein node Bin the existing WDS group is to join into another existing WDS group,and link with node A.

FIG. 4B shows the process flow of joining node B in the existing WDSgroup into another existing WDS group according to a preferredembodiment of the present invention.

FIG. 5 shows a schematic view of a wireless distribution system (WDS)network architecture.

FIG. 6 shows the process flow of distributional optimize according to apreferred embodiment of the present invention.

FIG. 7 shows the process flow of central control optimize according to apreferred embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The present invention provides a method for configuring a wirelessdistribution system (WDS). The steps of manual configuration can bereduced so as to optimize the WDS network performance. The protocolbuilt by the WDS provided in the present invention can add new WDS linksdynamically to realize the function of building WDS links between accesspoints (APs) automatically, and can perform optimization after the linkis built, so as to improve the use of the network resource. The contentof this protocol built by WDS comprises three parts of algorithm: (1)building a new WDS link; (2) incorporating the WDS network between nodesbelonging to two different groups; and (3) optimizing the WDS link.

Part One: Building a New Link

First, a new node B is to build a WDS link to a node A already existingin a WDS group. As shown in FIG. 3A, node B (i.e. AP B as shown) is tojoin into the existing WDS group, and linked with the node A (i.e. AP Aas shown, not the root node). The process of building a new linkincludes a scanning procedure, a building procedure and a joiningprocedure, which will be described in details referring to FIG. 3Bbelow.

First, the scanning procedure and the building procedure are defined.

Scanning procedure: The object of scanning is to discovery an AP thatcan be used for building WDS links, and the following parameters will beused:

ScanChannelList—the listed Channels required to be scanned, usually allthe Channels that can be supported;

MinChannelScanTime—the minimum time of scanning taken by each channel;

MaxChannelScanTime—the maximum time of scanning taken by each channel.

A ScanReport will be generated after the scanning is finished, in whichthe nodes can be used for building WDS links are listed. If theScanReport reports no node can be joined, each node will continue toscan or set itself as a Root node.

Building procedure: The object of building is to send WDS link buildinginformation, and wait for the reply message from the receiving terminaland then build the WDS link, and the following parameters will be used:

MinBuildingTime—the maximum time of building a WDS link.

MaxBuildingTime—the minimum time of building a WDS link.

AvailableLinks—the number of the links available.

Channeland AvailableChannel—the number of the channels available.

OtherInformation—other information, such as Root information or others.

The method for building the process flows will be described in detailsas follows with reference to the marked steps of FIG. 3B.

Scanning Procedure and Building Procedure:

Step 1: node A starts the building procedure and begins to broadcastbc_build signal, wherein the bc_build signal includes a Media AccessControl (MAC) address of node A, and a broadcasting time is set to bebetween MinBuildTime and MaxBuildTime. A new node B presses the buttonof reset, and starts the scanning procedure, which performs scanningaccording to the listed channels in the ScanChannelList, and thescanning time is between MinChannelScanTime and MaxChannelScanTime.

Step 2: after node B finishes scanning, a ScanReport is obtained, inwhich the scanned result is listed, and node B will choose the node tobe joined, which is node A according to this exemplary flow, accordingto its Join strategy, and locks the channel used by node A.

Joining Procedure:

Step 3: node B sends a connect request (i.e. “ConnectReq”, whichincludes a MAC address of node B) to node A.

Step 4: node A checks whether there is an available link or not. Ifthere is one link available, the MAC address of node B is stored to aninternal table of node A, which can be a WDS Table according to analternative embodiment. If there is no link available, it enters to theerror process, which will be described in FIG. 3C below. Step 5: if nodeA has an available link, it selects one link and assign it to node B,then send a ConnectRes signal to node B.

Step 6: node B sends a ChannelAssignReq signal to node A, for requestingnode A to assign a channel.

Step 7: node A selects an available channel.

Step 8: after node A selects the channel, it sends the ChannelRes signalto node B.

Step 9: node A stores the MAC address of node B to an internal tablethereof, which can be a WDS Table according to an alternativeembodiment.

Step 10: after node B receives ChannelRes, it stores the MAC address ofnode A to the WDS table and configures this designated link channel.

The above process of building a new link comprises a Scanning procedure,a Building procedure and a Joining procedure.

And if node B fails to join into an existing WDS group, refer to thedescription of building error of FIG. 3C.

Step 1: node A starts the building procedure and begins to broadcastbc_build, wherein the bc_build comprises the MAC address of node A, andthe broadcasting time is between MinBuildTime and MaxBuildTime. And newnode B presses the button of reset, and starts the scanning procedure,to scan according to the listed channels in the ScanChannelList, and thescanning time is between MinChannelScanTime and MaxChannelScanTime.

Step 2: after node B finishes scanning, a ScanReport is obtained, inwhich the scanned result is listed, and node B will choose the node tobe joined, which is node A according to this exemplary flow, accordingto its Join strategy, and locks the channel used by node A.

Step 3: node B sends a connect request (i.e. “ConnectReq”, whichcomprises the MAC address of node B) to node A.

Step 4: node A checks whether there is an available link nor not.

Step 5: if node A has no available link, it sends ConnectRes(Fail)message to node B.

Step 6: after node B receives the ConnectRes(Fail) message, itdiscoveries another node to be joined.

Part two: Building a WDS Link Between Two Nodes Built in Different WDSNetworks

The chance of occurring is that, the two nodes to be built already havewireless networks they belong to and Root Nodes, and have finished theoptimization. As shown in FIG. 4A, node A belongs to WDS Group 1, anduses channel 1; while node B1 belongs to WDS group 2, and uses channel6. If a link is to be built between node A and node B belonging todifferent WDS networks respectively, since the channels used by the twogroups are different, the building of WDS link will generate channelconflict, as well as the conflict between two root nodes.

In a preferred embodiment of the present invention, a method of how tobuild a WDS link between two nodes built in different WDS networks, andthe detailed process refers to FIG. 4B.

Step 1: node A starts the building procedure and begins to broadcastbc_build, wherein the bc_build comprises the MAC address of node A, andthe broadcasting time is between MinBuildTime and MaxBuildTime. And nodeB1 presses the button of reset and starts the scanning procedure, toscan according to listed channels in ScanChannelList, and the scanningtime is between MinChannelScanTime and MaxChannelScanTime.

Step 2: after node B1 finishes the scanning, a ScanReport is obtained,in which the scanned result is listed, and node B1 will choose node A tobe connected according to its Join strategy and lock the channel used bynode A.

Step 3: node B1 sends connect request (ConnectReq, which comprises theMAC address of node B1) to node A.

Step 4: node A checks whether there is an available link or not: ifthere is one, the MAC address of node B1 is stored into an internaltable of node A, which can be a WDS Table according to an alternativeembodiment.

Step 5: if node A has an available link, it selects a link and assignsit to node B1, then sends ConnectRes to node B1.

Step 6: node A stores the MAC address of node B1 into the WDS tablethereof. And node B1 also stores the MAC address of node A into theinternal table thereof, which can be a WDS Table according to analternative embodiment.

Step 7: node B1 sends ChannelReq to node A, requesting node A to assigna channel.

Step 8: node A selects an available channel.

Step 9: after node A selects the channel, it sends a ChannelRes to nodeB1.

Step 10: node B1 stores new channel and configures old channel.

Step 11: node B1 discoveries the occurrence of channel conflictaccording to the information sent by node A, and node B1 will unicastchannel conflict message to parent node or child node in its originalgroup, and request other nodes to change their channels. As shown in thedrawing, node B2 belonging to the same WDS group with node B1 will alsounicast the channel conflict message to parent node or child node whenit received the channel conflict message unicast by node B1.

Step 12: after node B1 unicasts the channel conflict message to parentnode or child node, configure a new channel. And the above node B2 willalso configure a new channel.

Step 13: node B1 notifies its group to set the root node to be the rootnode of group A.

Step 14: node B1 unicasts the message that the original root node hasbeen invalidated to parent node or child node.

Step 15: optimizes the root node sent to node A.

According to the above steps, a link can be built between node A andnode B1 belonging to different WDS networks, and the channels used bythe two groups will be the same, which will not cause the channelconflict, and the root node will be consistent.

Part Three: Optimize

The present invention provides an optimize method of wirelessdistribution system (WDS). This optimize method can use algorithmsemploying central control or distributional optimize. Referring to FIG.5, it shows a schematic view of WDS network architecture. As shown inthe drawing, under the root node (R), node A and node B belong to thesame layer, and node C and node D belong to the layer under node B,moreover, node C in turn belongs to the layer under node A, therefore, aLoop is generated. It will be described in combination of the WDSnetwork architecture in FIG. 5.

Distributional Optimize

The distributional optimize is directed to adjust the assignment ofinternal WDS links in a group, in order to avoid the generation of loopand the waste of resource. Referring to FIG. 6, and in combination withthe WDS network architecture of FIG. 5, the distributional optimizealgorithm in a preferred embodiment of the present invention isdescribed respectively with the interaction between nodes. And ROOT inthe drawing represents the root node.

First, root node ROOT notifies other nodes by unicast, requesting eachnode to adjust their channels to the same channel inMaxUCSameChannelTime, further, for example, each node will also unicastbc_sameChannel and bc_measurepacket in MaxBCSameChannelTime to collectadjacent information, such that the new nodes to be joined are optimizedat the same time. As shown, the root node sends SameChannel signal tonode A and node B, requesting them to adjust their channels to a samechannel, and node B sends the signal to node C and node D to carry outthe SameChannel adjustment. Further, bc_sameChannel signal andbc_measurepacket signal are also sent to node A˜D to collect theadjacent information. This is shown as in the channel adjustmentnotification period marked in the right part of the drawing.

Thereafter, root node broadcasts optimize command bc_optimize inMaxBCOptimizeTime, comprising the available channels and the number oflinks for the root node, power of the root node, other information andthe like. After the member has received bc_optimize, it will have itsown message appended to the bc_optimize packet and continue tobroadcast. After MaxBcOptimeTime is finished, each node will select apreferable parent node according to the message in the receivedbc_optimize packet.

Referring to FIG. 6, root node ROOT broadcasts the optimize commandbc_optimize[R], wherein [R] represents the available channels and thenumber of links for the root node, power of the root node, otherinformation and the like. After bc_optimize[R] is sent to node A andnode B, node B broadcasts optimize command bc_optimize[RB] to node C andnode D, wherein [RB] indicates that besides the available channels andthe number of links for the root node, power of the root node, otherinformation and the like, the message of node B is further appended tothe bc_optimize packet and it will continue to broadcast.

Thereafter, in the same manner, node C broadcast optimize commandbc_optimize[RBC] to other nodes, for example node D, wherein [RBC]indicates that besides the available channels and the number of linksfor the root node, power of the root node, other information and thelike, the message of node C is further appended to the bc_optimizepacket and it will continue to broadcast. And node D broadcasts optimizecommand bc_optimize[RBCD] to other nodes, for example node B and node C,wherein [RBCD] indicates that besides the available channels and thenumber of links for the root node, power of the root node, otherinformation and the like, the message of node D is further appended tothe bc_optimize packet and it will continue to broadcast. This is shownas in the optimized message notification period marked in the right partof the drawing.

Thereafter, the selection of Parent node is carried out, then theJoining procedure as described in Part one is carried out. This is asshown in the internal table of adjusting as marked in the right part ofthe drawing, which can be the WDS Table thereof according to analternative embodiment, and channel adjusting period. All nodes A, B, Cand D and the like are joined into the WDS network architecture underthe root directory.

Central Control Optimize

The object of central control optimize is the same as that of thedistributional optimize, and is to allow the root node to discovery aWDS path optimized for the whole network.

Referring to FIG. 7, and in combination with the WDS networkarchitecture of FIG. 5, the central control optimize algorithm of apreferred embodiment of the present invention is described respectivelywith the interactions between nodes. And ROOT in the drawings representsroot node. First, the root node (Root) notifies other nodes bybroadcast, requesting each node to adjust to a same channel inMaxUCSameChannelTime, besides, each node will also in turn broadcastbc_measurepacket to collect adjacent information, and prepare to performcentral control optimize.

As shown, the root node sends SameChannel signal to node A and node B,requesting them to adjust their channels to the same channel, and node Bsends the signal to node C and node D, to perform the SameChanneladjustment. Further, bc_measurepacket signal is then sent to nodes A˜Dto collect the adjacent information. This is shown as in the channeladjustment notification period marked in the right part of the drawing.

Thereafter, the root node ROOT sends Discovery message and returnsDiscovery acknowledge (as marked as ack in the drawing) through nodes,to give the resource and information of each node, including themessages of channel, power, link etc. As shown in FIG. 6, the root nodesends discovery signal to node A and node B, requesting for the resourceand information of each node, and then node A and node B reply the acksignal to the root directory ROOT respectively. And node B sendsDiscovery message to node C and node D, requesting for the resource andinformation of each node, and then node C and node D reply the acksignal to node B respectively.

Then, each node that has received the Discovery message will send theresource and information of itself, including the messages of channel,power, link etc, to the node sending the message with a “reply” signal,and then, it will receive a “reply ack” signal. As shown in FIG. 7, theroot node ROOT sends a discovery signal to node A and node B, then, nodeA and node B will send their messages back to the root node ROOT with a“reply” signal, and the root node ROOT will in turn send a “reply ack”signal back to node A and node B. The node B sends a discovery signal tonode C and node D, then, node C and node D will send their messages backto node B with a “reply” signal, and node B will in turn send a “replyack” signal back to node C and node D. This is shown as in theinformation return period marked in right part of the drawing.

Then, the root node ROOT performs optimize calculation and sends theresult to each node. Each node changes its internal table, which can bethe WDS Table according to an alternative embodiment, according to themessage sent by the root node, and rebuilds a WDS link, to realize theoptimized configuration.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following and their equivalents.

1. A method for configuring a wireless distribution system, the methodcomprising: starting a building procedure and beginning to broadcast abuilding information by a target node, wherein the building informationcomprises a media access control (MAC) address of the target node;starting a scanning procedure by a joining node, to obtain and lock thetarget node; sending a connect request signal to the target node by thejoining node; selecting an available link by the target node if thetarget node has at least one or more available links, assigning theselected link to the joining node and then sending a connect acknowledgesignal to the joining node; sending a channel assign request to thetarget node by the joining node, and requesting the target node toassign a channel; selecting the channel by the target node and sending achannel reset signal to the joining node, and storing a MAC address ofthe joining node into an internal table of the target node; and afterreceiving the channel reset signal by the joining node, storing the MACaddress of the target node into an internal table of the joining node,and configuring the channel; and if the target node has no availablelink to be assigned to the joining node, a ConnectRes(Fail) signal issent by the target node to the joining node, and the target node and thejoining node can not communicate with each other.
 2. The method of claim1, wherein the scanning procedure of the joining node performs scanningto all the channels listed in a scan channel list, and after a scanreport is obtained, obtains and locks one channel used by the targetnode according to the scan report.
 3. A method for configuring awireless distribution system, the method comprising: starting a buildingprocedure and beginning to broadcast a building information by a targetnode belonging to a first wireless distribution system network, whereinthe building information comprises a MAC address of the target node;starting a scanning procedure by a joining node belonging to a secondwireless distribution system network, to obtain and lock the targetnode; sending a connect request signal to the target node by the joiningnode; selecting a link and assigning the link to the joining node by thetarget node, and then sending a connect acknowledge signal to thejoining node; sending a channel assign request to the target node by thejoining node, and requesting the target node to assign a channel;selecting the channel by the target node and sending a channel resetsignal to the joining node, and storing a MAC address of the joiningnode into an internal table of the target node; and after receiving thechannel reset signal by the joining node, storing the MAC address of thetarget node into an internal table of the joining node, and configuringthe channel; wherein if the joining node discoveries an occurrence ofchannel conflict according to the channel reset signal of the targetnode, the joining node unicasts a channel conflict message to othernodes in the second wireless distribution system network for requestingthe other nodes to change their channels, and the other nodes that havereceived the channel conflict message also in turn unicast the channelconflict message, and the joining node further requests the other nodesto set a root node of the first wireless distribution system network asa root node of the second wireless distribution system network.
 4. Themethod of claim 3, wherein the scanning procedure of joining nodeperforms scanning to all the channels listed in a scan channel list, andafter a scan report is obtained, obtains and locks one channel used bythe target node according to the scan report.
 5. The method of claim 3,wherein if the target node has no available link to be assigned to thejoining node, a ConnectRes(Fail) signal is sent by the target node tothe joining node, and the target node and the joining node can notcommunicate with each other.